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Rectification of the channelrhodopsin early conductance.
Gradmann D, Berndt A, Schneider F, Hegemann P.
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We analyzed the nonlinear current-voltage relationships of the early conducting state of channelrhodopsin-2 expressed in Xenopus oocytes and human embryonic kidney cells with respect to changes of the electrochemical gradients of H(+), Na(+)/K(+), and Ca(2+)/Mg(2+). Several models were tested for wild-type ChR2 and mutations at positions E90, E123, H134, and T159. Voltage-gating was excluded as cause for the nonlinearity. However, a general enzyme kinetic model with one predominant binding site yielded good fits throughout. The empty site with an apparent charge number of about -0.3 and strong external cation binding causes some inward rectification of the uniport function. Additional inward rectification is due to asymmetric competition from outside between the transported ion species. Significant improvement of the fits was achieved by introducing an elastic voltage-divider formed by the voltage-sensitive barriers.
Andersen,
Kinetics of ion movement mediated by carriers and channels.
1989, Pubmed
Andersen,
Kinetics of ion movement mediated by carriers and channels.
1989,
Pubmed Barish,
A transient calcium-dependent chloride current in the immature Xenopus oocyte.
1983,
Pubmed
,
Xenbase Berndt,
High-efficiency channelrhodopsins for fast neuronal stimulation at low light levels.
2011,
Pubmed Berndt,
Two open states with progressive proton selectivities in the branched channelrhodopsin-2 photocycle.
2010,
Pubmed
,
Xenbase Blatt,
Interpretation of steady-state current-voltage curves: consequences and implications of current subtraction in transport studies.
1986,
Pubmed Dieckmann,
Exploration of the structural features defining the conduction properties of a synthetic ion channel.
1999,
Pubmed Facciotti,
Structure of an early intermediate in the M-state phase of the bacteriorhodopsin photocycle.
2001,
Pubmed Feldbauer,
Channelrhodopsin-2 is a leaky proton pump.
2009,
Pubmed Gradmann,
Apparent charge of binding site in ion-translocating enzymes: kinetic impact.
2005,
Pubmed Gradmann,
Reaction kinetic parameters for ion transport from steady-state current-voltage curves.
1987,
Pubmed Gunaydin,
Ultrafast optogenetic control.
2010,
Pubmed
,
Xenbase Hagedorn,
Dynamics of voltage profile in enzymatic ion transporters, demonstrated in electrokinetics of proton pumping rhodopsin.
2008,
Pubmed Hansen,
Interpretation of current-voltage relationships for "active" ion transport systems: I. Steady-state reaction-kinetic analysis of class-I mechanisms.
1981,
Pubmed Hegemann,
Algal sensory photoreceptors.
2008,
Pubmed Hegemann,
Multiple photocycles of channelrhodopsin.
2005,
Pubmed
,
Xenbase Hill,
Studies in irreversible thermodynamics. IV. Diagrammatic representation of steady state fluxes for unimolecular systems.
1966,
Pubmed Lin,
Characterization of engineered channelrhodopsin variants with improved properties and kinetics.
2009,
Pubmed
,
Xenbase Lu,
Mechanism of rectification in inward-rectifier K+ channels.
2004,
Pubmed Nagel,
Channelrhodopsin-2, a directly light-gated cation-selective membrane channel.
2003,
Pubmed
,
Xenbase Nagel,
Channelrhodopsin-1: a light-gated proton channel in green algae.
2002,
Pubmed
,
Xenbase Neher,
Correction for liquid junction potentials in patch clamp experiments.
1992,
Pubmed Nelson,
A permeation theory for single-file ion channels: one- and two-step models.
2011,
Pubmed Nikolic,
Modeling and engineering aspects of channelrhodopsin2 system for neural photostimulation.
2006,
Pubmed Nikolic,
Photocycles of channelrhodopsin-2.
2009,
Pubmed Roux,
Ion conduction and selectivity in K(+) channels.
2005,
Pubmed Ruffert,
Glutamate residue 90 in the predicted transmembrane domain 2 is crucial for cation flux through channelrhodopsin 2.
2011,
Pubmed
,
Xenbase Schoenenberger,
Channelrhodopsin as a tool to investigate synaptic transmission and plasticity.
2011,
Pubmed Tsunoda,
Glu 87 of channelrhodopsin-1 causes pH-dependent color tuning and fast photocurrent inactivation.
2009,
Pubmed Woodhull,
Ionic blockage of sodium channels in nerve.
1973,
Pubmed Zhang,
Red-shifted optogenetic excitation: a tool for fast neural control derived from Volvox carteri.
2008,
Pubmed
,
Xenbase
